Gust lock



Oct. 9, 1951 J. P. NIX 2,570,586

GUST LOCK Filed April 6, 1946 4 Sheets-Sheet 1 INVENTOR.

JOHN P. NIX

ATTORNEY Oct. 9, 1951 J p, NIX 2,570,586

GUST LOCK Filed April 6, 1946 v 4 Sheefis-Sheet 2 FIG.3

INVENTOR.

JOHN P. NIX BY 6* @AJW. M

ATTORNEY J. P; NIX

GUST LOCK Oct. 9, 1951 -4 Sheets-Sheet 3 Filed April 6, 1946 INVENTOR.

JOHN P. NIX

ATTORNEY Oct. 9, 1951 J, Nlx 2,570,586

GUST LOCK Filed April 6, 1946 4 Sheets-Sheet 4 INVENTOR.

JOHN P. NIX

Patented Oct. 9, 1951 UNITED PATENT OFFICE John P.; Nix; Normandy, Mo.-,- assignfor to Gurtiss Wright corporation, a corporation of D'elat Application A ril 6; 1946", Serial No'. 660,164

reclaims;

1 l This invention relates to locking devices for control surfaces of aircraft and more artiem' iv to the type of locking devices known as gust locks for efiectively locking such surfaces a new trail position against movementby gusts while the-airplane-ison the ground:

Y Gust locksof this general type heretofore known have provided locking means for control surfaces either with or without spring tabs; These devices usually comprise a mechanism for locking" thesurface in a neutral position, the mechanism ,being movedinto locked or unlocked position by means independent of the primary control system operated by the pilot. Locks of this: type provide a hazard in that the pilot may inadvertently neglect to unlock the mechanism before a takeofi; thus endangering the airplane. The present invention provides a gust lock, which may be selectively locked or unlocked by the" pilot from theco'ckp'it, and which eliminates thehazard of taking-01f with locked controls by incorporatmg' means whereby the lock, if applied, automatically released." by the 'pilots 'normal movement of the primary control system.

In certain control systems having aspring tab, the" primary controls operatedbythe pilot are connected directly to the tab and to" the main control surface only through spring means; In such" a' system a' gust lock applied to the primary controls has thedisadvantagethat air gust loads can move the" control surface to the limit allowed hy'the spring: means" or stops associated there With. 7

This invention overcomes this disadvantage by providing means for directly locking the main control surface, leavin only" the relatively small tab susceptible to movements by gust loads'l'ima Red in degree by" the spring means and associated stops.

' Itistherefore the p'rinraryobject of this inven-' tion to provide a locking" mechanism for a con trol surface of an airplane which is releasable by the pilot upon normal operation of theprimary'controls.

Another object is found. in the provision of a gustlock for control surfaces having spring tabs operated'in' connection therewith which maybe locked or 'unlocked'by a secondary pilot operable means, yt may be automatically unlocked the" pilot operated primary control means in its normalop'erati'ngfunction.

Ali additional Object resides iiifth'e" provision of'a' gust lock mechanism for effectively mainthereto at it.

2 be unlocked by the pilot operated primary con trols, yet is so arranged and constructed that gustload's on the combined surface and tab, particularly the tab, will not efiect release of the locking mechanism.

The foregoing and other objects and advantages-will become apparent from the'followingdetailed description and accompanying drawings in which:

Figure I is a diagrammatic elevational view illustrating anapplication of the gustlockof the present invention to the stabilizer, elevator, and spring tab of an aircraft;

Figure 2' is a perspective view of the locking mechanism pe'rse.

Figure 3 is an enlarged elevation'al view er the lockingmechanism inits neutral locked} condition.

Figure 4- is a similar view showing the limit position of the locked parts for a down-gust load on the control surface and tab.

Figure 5 is a similar view showing the limit position of the locked parts for an l p-gust load on thesurface and tab.

Fig'u-refi is asimilar view showing the unlocked neutral position of the parts; 7

Figures 7 and 8 are similar views showing" the position of parts during up-elevator and downelevator positions, respectively, when the mechanism i-sin unlockedcondition.

While the gust lock mechanism of this lnven tion is shown in the drawings and will be de'-' scribed hereafter as applied to an elevator and tab associated with the horizontal stabilizer of an aircraft, it will be understood that-itmay also be applied toother control surf-aces such as a rudder, aileron; or elevon.

'The gust lock unit constructed according to this invention and indicated generally at [his located inthehorizontal stabilizer H of the airplane. The elevator l3; hing-ed at M to the rear portion of the stabilizer, carriesa tab I 5, pivoted A lever l1 pivoted at theaxis of the elevator hinge I4 is connected at one end to tab horn- Hi' by link l9 and at its other end by link 23 to a control lever 21* suitably pivoted to the stabilizer structure at 22. Cable's-2 3 attachedto the lever 2 extend to the control column in the pilotscompartment in the usual manner. Spring's'Zo-operatively connect the lever H to the elevator and together with stops 2? engag'e'able I by the lever comprise a usual type ofspring' taining a' control surface having -ar1 associated" 7 spring" tab a loekedcondition and whichmay elevator operating connection. With an'arrange-* rhent ofthis kind, in the' absence ofrlar'geair loads the pilotsrnovement ofthe controlcables 23 will directly result in movement of elevator |3. In the presence of substantial air loads resisting movement of the elevator, the springs 26, 26 may fiex, causing movement of tab I relative to the elevator in a direction such that air pressures upon the tab will assist the pilot in moving the elevator.

The actual locking ortion of the gustlock unit In comprises an angular arm 30, a bell crank 3|, and an elevator connecting link 32. Arm 30 is pivotally mounted near one end of a pivot 33 fixed with respect to the stabilizer structure U and pivotally connected at its opposite end to the bell crank 3| as shown at 34. A portion 35 of the arm so extends below pivot 33 as to normally engage a fixed stop pin 35 and has connected thereto one end of a spring 31, the opposite end of which is attached to an extension 38 of bell crank 3|. Link 32 is pivotally attached to the elevator at 40 and isconnected at its opposite end by pivot pin 39 to one arm of the bell crank 3|. A stop portion 42 on bell crank 3| is positioned for engagement with link 32 to limit the angular movement of these two parts under certain conditions as hereinafter described. Pivotally attached to the upright arm of bell crank 3| by bolt 43 is an operating link 44 which is connected at its opposite end at 45 to a radial arm 46 carried by a pulley 41 mounted on the fuselage or other fixed part of the aircraft. A cable system 48, which may 'be termed a secondary lock control system, operatively connects pulley 41 with suitable means (not shown) for manual operation in the p-ilots compartment.

Arms and 30, triangular member 58 and link 59 are so proportioned as to constitute a paral lelogram linkage. Movement of this linkage relative to the bell crank 3| is restricted in one direction by stop roller 56 engaging arm 30 at 51 for the purpose hereintofore described, and is restricted in the opposite direction by a roller 69 carried by triangular member 58 engaging stop 6| formedon the bell crank.

The length of the bell crank 3| between pivot centers 34 and 43 is equal to the length of arm 30 between pivot centers 33 and 34 so that in one relative position of these parts, as appears in Figures 6, 7 and 8, the pivots 33 and 43 are in coaxial relation, the parts being so held by spring 31 whose line of tension is above pivot 34. i

A pin 5| extends from bellcrank 3| into the path of arm 33 and engages the latter to determine this limit position of the parts 30 and 3|. It will be noted that when members 36 and 3| are so moved relatively that the tension line of the spring 31 passes below pivot 34, the spring will urge a movement of the membersthat will further separatepivots 33 and 44, this being the condition in Figures 1 to 5.

As to operation of the mechanism, it will first be noted from Figure 1 that when the gust lock mechanism -|0 holds locking link 32 against movement, a down gust load on the elevator I3 and tab l5 will place link 32 under compression, urging it toward the left, while the link 53 will be placed in tension, urging it also to the left.

sisted by springs 26, 26 and limited by engagement of lever I1 with stops 21, 21.

It will also be noted that starting with the parts in locked position, movement of the tab and elevator by the pilot through the primary control cables 23, 23 will apply forces to link 53 which are reversed with respect to those produced by gust loads. Clockwise movement of control lever 2| to move the elevator down will move lever 53 to the right and, through springs 26 or stop 21, will urge or effect movement of link 32 toward the left. Similarly counterclockwise, or up-elevator, movement of control lever 2| will move link 53 to the left and urge or effect movement to the right of link 32.

Starting with the locked position shown in Figures 1 and 3 and assuming gust loads insufficient to move tab |5 against the resistance of springs 26, 26, it will be seen that a down gust load on elevator 13, urging link 32 toward the left, will urge arm 30 counterclockwise against fixed stop 36 because pivot 39 is disposed above the line between pivot points 33 and 40, the pivot 39 being held there by spring 31 urging bell crank 3| clockwise about pivot 34. Accordingly, the thrust applied to link 32 will be transmitted to fixed pivot 33, and the elevator will be held against down movement. An up gust insufiic'ient to move the tab also will leave the parts substantially in the condition shown in Figure 3, the pull to the right of'link 32 further urging clockwise movement of bell crank 3| about pivot 34 to hold stop 42 against link 32, and being transmitted through arm 30 to fixed pivot 33. Accordingly, the elevator will be held against up-movement in response to the up gust load.

Considering next a down gust load on the elevator-tab assembly of sufficient magnitude to move the tab to the limit allowed by right stop 21, link 53 will be moved to the left to the position shown in Figure 4. Bell crank 3| will be swung counterclockwise about pivot 34 to the position shown by roller 60 of member 58 which is swung counterclockwise in parallelism to arm 55 because of connecting link 59. Since thrust applied by link 32 at pivot 39 produces a clockwise movement of the bell crank, holding stop 6| against roller 60, members 3| and 58 in effect become a unit which the thrust of link 32 tends to swing upwardly about the pivot that connects members 58 and 59. The resultant upward force at pivot 34 holds the arm 30 against fixed stop 36. Therefore, since the thrust of link 32 cannot result in motion, the elevator is locked against down motion. It will be noted that under this condition the tension line of spring 31 is beneath the pivot 34, further tending to hold arm 3!) and bell crank 3| in the relationship shown in Figure 4. f

Considering next an up gust load on the elevator-tab assembly suflicient to move the tab to the limit allowed by left stop 21, which will cause link 53 to move to the right to the position shown in Figure 5, it will be seen that the arm 55 hasb'een swung clockwise about fixed pivot 33. By'reason of roller 56 engaging stop 51, the arm 30 has also been moved clockwise, lowering pivot 34. As the latter is below the line 39, 40 pull on the link 32 produced bythe up-gust load on the elevator will urge the bell crank 3| clockwise about pivot 34, holding stop 42 against link 32, and will urge arm 30 counterclockwise to abut stop 51 with roller 56. Since the arm 55 carrying this roller is being held by the thrust of link 53 which displaced it from the neutral position of Figure 4, counter- Referring next to the unlockedneutral'position clockwise motion of arm 30 is prevented and the pull of link 32 is transmitted to the fixed pivot 33, looking the elevator against up-movement.

ofthe parts, asshow nin Figure 6, resulting fromcounterclockwise movement of pulley 41 and arm 46 by the pilots operation of lock control cable 48, the consequent movement of link 44 to the left has swung bell crank 3| counterclockwise about pivot 34 sufficiently to place the tension line of spring 31 above the pivot 34. Accordingly, the bell crank and arm 30' are relatively moved to bring pivots 33 and 43 into coaxial: relation, as shown.

During subsequent movement of the elevator and tab the bell crank and arm 30 may move as a unit about the axis of fixed pivot 33 as the link 32 moves to the right or left in response to up or down movement of the elevator, as shown in Figures '7 and 8, respectively. During such movement the remainder of the parallelogram linkage comprising parts 58 and 59 will move freely in accordance with the relative movements of arms 30 and 55, the latter swinging freely about the .fixed pivot 33 as the result of link con-' nection 53 to the operating lever 2|.

Should the airplane take off. with the control lock. applied, normal movement of the elevator control system will immediately release the look. If the pilot applies a down-elevator movement, swinging the control lever 2| clockwise, link 53 will be moved to the right from the position shown in Figure 3, while the link 32 will be. urged toward the left. As a result arm 30 will be swung clockwise to lower pivot 34 and raise extension 35 sufiiciently that the line of tension of spring 31 will pass above pivot 34, whereupon the pivot 43 will swing into coaxial relation with fixed pivot 33,v allowing the parts to. move into: the down-elevator position shown in Figure 8.

'Should the pilot apply an up-elevator movement with the control lock applied, swinging control lever 2| counterclockwise, link 53 will be moved to the left from the position shown in Figure 3, while the link. 32 will be urged to the right.

Resulting up-movement of roller 60 carried by 5 member 58 (see Fig. 4) combined with the pull Of'link 32' will swing bell crank 3| counterclockwise sufficiently to bring the tension line of spring 31 .above the pivot 34, whereupon the parts may move to a position substantially as shown in Figure 7, representing the full up -elevator condition. r

It will now be seen that the locking mechanism of this invention provides an effective control surface lock against gust loads, yet may be readi- 1y unlocked or releasedby the primary pilot controls without unduly affecting the operation thereof or imposing any appreciable additional loads thereon.

f It will be understood that the mechanism here-. in specifically described is merely illustrative of theinventive principles involved, and that these principles may be otherwise embodied without departing from the spirit of the invention or th scope of the appended claims.

I claim: 7 1. In an aircraft, a movable element andoperating means therefor having a resilient. play connection thereto;- locking means for said element comprising a first member connected by a first pivot to the aircraft, a second member connected to the first member by a second pivot, a link connected to the second member by a third pivot and by'afourth pivot to said element, and resilient means connecting said members to urge them about the second pivot intoa locking relationship wherein the pivots are substantially aligned for holding the element against movement-or to' urge 6 the members into an unlocked relationship wherein the third pivot is remote from a line be-- tween the first and fourth pivots for permitting said members to swing about the first pivot in response to movement of the element; lock control means for moving said members into either of said relationships; and means operable by and upon actuation of the operating means for moving the members into their unlocked relationship.

2. In an aircraft, a movable control surface having an auxiliary surface movably connected thereto; operating means for said auxiliary sur face and a resilient play connection between said surfaces whereby the control surface may also be moved by the operating means; locking means for the control surface comprising a mom-'- ber connected by a first pivot to the aircraft and to a second member by a second pivot, a link connected by a third pivot to the second member and by a fourth pivot to the control surface, and resilient means connecting said members to urge them about the second pivot either into a locking relationship wherein the pivots are substantially aligned or into an unlocked relationship wherein the third pivot is remote fromaline between the first and fourth pivots permitting saidmembers to swing about the first pivot in response to movement of the element; lock control means for moving said members into either of said relationships; and means operable by and upon actuation of the operating means for moving the members into their unlocked relationship.

3. In a locking mechanism for an aircraft having a movable element actuated by operat ing means through a resilient play connection,- afirst member having a pivot connection to theaircraft, a second member pivoted to the first member and also pivoted to a link connected to said element, said members being relatively movable about their common pivot between a first relationship wherein the link is held against substantial movement relative to said pivot connection and a second relationship wherein the members may swing as a unit about said pivot connection upon movement of the link, lockcontrol means connected to the second member for effecting relative movement of said membersinto either of said relationships, and means operable by and upon actuation of said operating means when said members are in said first relation-- ship for effecting relative movement of said members into the second relationship. I

i. In a locking mechanism for an aircraftha'v ing a movable element actuated by operating means through a resilient play connection, a first member having a pivot connection to the aircraft, a second member pivoted to the first member and also pivoted to a link connected to said element, said members being relatively m0v'-' able about their common axis between a first relationship wherein the link is held against substantial movement relative to the aircraft and a second relationship wherein the members may swing as a unit about said pivot connection upon movement of the link, resilient means for urging retention of the members in either of said relationships, lock control means connected to-the second member for effecting relative movement of said members into either of said relationships, and means operable by and upon actuation of said operating means when saidmembers are in said first relationship for effecting relative movement of said members into thesecond' relationship.

Y 5'. In a locking mechanism for an aircraft-hay ing a movable element actuated by'operating means through a resilient play connection, a first member-having a pivot connection to the aircraft, a second member pivoted to the first member and also pivoted to a link connected to said element, said members being relatively movable about their common pivot between a first relationship wherein the link is held against substantial movement relative to said pivot connection and a second relationship wherein the members may swing as a unit about the pivot to the aircraft upon movement of the link, lock control means connected to the second member for effecting relative movement of said members into either of said relationships, said lock control means being pivotally connected to the second member coaxially with said pivot connection when the members are in the second relationship, and means operable by and upon actuation of said operating means when said members are in said first relationship for effecting relative movement of said members into the second relationship.

6. In a locking mechanism for an aircraft having a movable element actuated by operatingmeans through a resilient play connection, a first member having a pivot connection tothe aircraft, a second member pivoted to the first member and also pivoted to a link connected to said element, said members being relatively movable about their common axis between a first relationship wherein the link is held against substantial movement relative to the aircraft and a second relationship wherein the members may swing as a unit about said pivot connection upon movement of the link, resilient means for urging retention of the members in either of said relationships, lock control means connected to the second member for effecting relative movement of said members into either of said relationships, said lock control means being pivotally connected to the second member coaxially with said pivot connection when the members are in the second relationship, and means operable by and upon actuation of said operating means when said members are in said first relationship for efiecting relative movement of said members into the second relationship.

7. In an aircraft, a movable control surface having an auxiliary surface movably connected thereto, operating means for moving said auxiliary surface, a resilient play connection between said surfaces by which the control surface may be moved by the operating means in an opposite direction from the auxiliary surface, a first member having a pivot connection to the aircraft, a second member pivoted to the first member and to a link connected to said control surface, said members being relatively movable between a first relationship wherein the link is held against substantial movement and a second relationship wherein the members may swing about the pivot to allow movement of the link, lock control means connected to the second member for effecting movement of the members intoeither of said relationships, and means operable by and upon actuation of said operating means when the members are in said first relationship for effecting relative movement of the members into the second relationship.

3. In an aircraft, a movable control surface having an auxiliary surface movably connected thereto; operating means for said auxiliary surface and a resilient play connection between said surfaces whereby the control surface may also be moved by the operating means; locking means for the control surface comprising a, first member connected by a first pivot to the aircraft and to a second member by a second pivot, a link connected by a third pivot to-the second member and by a fourth pivot to the control surface, and resilient means connecting said members to urge them either into a locking relationship wherein the pivots are substantially aligned or into an unlocked relationship wherein the third pivot is remote from a line between the first and fourth pivots permitting said members to swing about the first pivot in response to movement of the control surface; lock control means for moving said members into either of said relationships, said lock control means being pivotally connected to the second member on a pivot axi which is substantially coincident with said first pivot when the members are in the unlocked relationship; and means operable by and upon actuation of the operating means for moving the members into the unlocked relationship.

9. In an aircraft, a movable control surface having an auxiliary surface movably connected thereto; Operating means for said auxiliary surface and a resilient play connection between said surfaces whereby the control surface may also be moved by the operating means; locking means for the control surface comprising a; first member connected by a first pivot to the aircraft and to a second member by a second pivot, a, link connected by a third pivot to the second member and by a fourth pivot to the control surface, and resilient means connecting said members to urge them either into a locking relationship wherein the pivots are substantially aligned or into an unlocked relationship wherein the third pivot is remote from a line between the first and fourth pivots permitting said members to swing about the first pivot in response to movement of the control surface; lock control means for moving said members into either of said relationships; and unlocking means operable by and upon actuation of the operating means for moving the members into the unlocked relationship, said unlocking means including a part engageable with the first member to move the latter about the first pivot, upon actuation of the operating means in one direction, to effect relative movement of the members into the unlocked relationship, and said unlocking means also including another part engageable with the second member to move the latter about the second pivot, upon actuation of the operating means in the opposite direction, to effect relative movement of the members into the unlocked relationship.

10. In an aircraft, a movable control surface having an auxiliary surface movably connected thereto; operating means for said auxiliary surface and a resilient play connection between said surfaces whereby the control surface may also be moved by the operating means; locking means for the control surface comprising a first member connected by a first pivot to the aircraft and to a second member by a second pivot, a link connected by a third pivot to the second member and by a fourth pivot to the control surface, and resilient means connecting said members to urge them either into a locking relationship wherein the pivots are substantially aligned or into an unlocked relationship wherein the third pivot is re mote from a line between the first and fourth pivots permitting said members to swing about the first pivot: in response to movement of the control surface; lock control means for moving saidlmem'bersinto ,either,of said relationships; and unlocking means operable by and upon actuation of the operating-means for moving the members into their unlocked relationship, said unlocking means comprising two parts interconnected by a pivoted link and arranged for angular movement respectively about said first and second pivots, one of said parts engaging and moving the first member. into said unlocked relationship upon actuation of .said operating means in one direction, and the other of said parts ongaging and moving the second member into said unlocked relationship upon actuation of said operating means in the opposite direction.

11. In an aircraft, a movable control surface having an auxiliary surface movably connected thereto; operating means for said auxiliary surface and a resilient play cormection between said surfaces whereby the control surface may also be moved by the operating means; locking means for the control surface comprising a first member connected by a first pivot to the aircraft and to a second member by a second pivot, a link connected by a third pivot to the second member and by a fourth pivot to the control Surface, and resilient means connecting said members to urge them either into a locking relationship wherein the pivots are substantially aligned or into an unlocked relationship wherein the third pivot is remote from .a line between the first and fourth pivots permitting said members to swing about the first pivot in response to movement of the control surfaceylook control means for moving said members into either of said relationships, said lock control means being pi-votally connected to the second member on an axis that is coaxial with said first pivot when the members are in unlocked relationship; and unlocking means operable by and upon actuation of the operating means for moving the members into their unlocked relationship, said unlocking means including a part engageable with the first member to movethe'latter about the first pivot, upon actuationof the operating means in one direction, to effect relative movement of the members into their unlocked relationship, and said unlocking means also including another part engageable with the second member to move the latter about the second pivot, upon actuation of the operating means in the opposite direction, to effect relative movement of the members into their unlocked relationship.

12. In an aircraft, a movable control surface having an auxiliary surface movably connected thereto; operating means for said auxiliary surface and a resilient play connection between said surfaces whereby the control surface may also be moved by the operating means; locking means for the control surface comprising a first member connected by a first pivot to the aircraft and to a second member by a second pivot, a link connected by a third pivot to the second member and by a fourth pivot to the control surface, and resilient means connecting said members to urge them either into a locking relationship wherein the pivots are substantially aligned or into an unlocked relationship wherein the third pivot is remote from a line between the first and fourth pivots permitting said members to swing about the first pivot in response to movement of the control surface; and unlocking means operable by and upon actuation of the operating means for moving the members into their unlocked relationship, said unlocking means including a part engageablfi With the first member 10 to move the latter about the first pivot, upon actuation of the operating means in one direction, to effect relative movement of the members into their unlocked relationship, and said unlocking means also including another part engageable with the second member to move the latter about the second pivot, upon actuation of the operating means in the opposite direction,

to effect relative movement of the members into their unlocked relationship.

13. In an aircraft, a movable control surface, operating means for said surface connected thereto by a resilient play connection; locking means for the control surface comprising a first member connected by a first pivot to the aircraft and to a second member by a second pivot, alink connected by a third pivot to the second member and by a fourth pivot to the control surface, and resilient means connecting said members to urge them either into a locking relationship wherein the pivots are substantially aligned or into an unlocked relationship wherein the third pivot is remote from a line between the first and fourth pivots permitting said members to swing about the first pivot in response to movement of the control surface; lock control means for moving said members into either of sa d relationships; and unlocking means operable by and upon actuation of the operating means for moving the members into their unlocked relationship, said unlocking means including a part engageable with the first member .to move the latter about the first pivot, upon actuation of the operating means in one direction, to eifect relative movement of the members into their unlocked relationship, and said unlocking means also including another part engageable with the second member to move the latter about the second pivot, upon actuation of the operating means in the opposite direction, to effect relative movement of the members into their unlocked relationship.

14. In an aircraft, a movable control surface, operating means for said surface connected thereto by a resilient play connection; locking means for the control surface comprising a first member connected by a first pivot to the aircraft and to a second member by a second pivot, a link connected by a third pivot to the second member and by a fourth pivot to the control surface, and resilient means connecting said members to urge them either into a locking relationship wherein the pivots are substantially aligned or into an unlocked relationship wherein the third pivot is remote from a line between the first and fourth pivots permitting said members to swing about the first pivot in response to movement of the control surface; lock control means for moving said members into either of said relationships; and unlocking means operable by and upon actuation of the operating means for moving the members into their unlocked relationship, said unlocking means comprising two parts interconnected by a pivoted link and arranged for angular movement respectively about said first and second pivots, one of said parts engaging and moving the first member into said unlocked relationship upon actuation of said operating means in one direction, and the other of said parts engaging and moving the second member into said unlocked relationship upon actuation of said operating means in the opposite direction.

15. In an aircraft, a movable control surface, operating means for said surface connected thereto by a resilient play connection; locking means'for the control surface comprising a first member connected by a first pivot to the aircraft and to a second member by a second pivot, a link connected by a third pivot to the second member and by a fourth pivot to the control surface, and resilient means connecting said members to urge them either into a locking relationship wherein the pivots are substantially aligned or into an unlocked relationship wherein the third pivot is remote from a line between the first and fourth pivots permitting said members to swing about the first pivot in response to movement of the control surface; lock control means for moving said members into either of said relationships, said lock control means being pivotally connected to the second member on an axis that is coaxial with said first pivot where the members are in unlocked relationship; and unlocking mean operable by and upon actuation of the operating means for moving the members into their unlocked relationship, said unlocking means including a part engageable with the first member to move the latter about the first pivot, upon actuation of the operating means in one direction, to efiect relative movement of the members into their unlocked relationship, and said unlocking means also including another part engageable with the second member to move the latter about the second pivot, upon actuation of the operating means in the opposite direction, to effect relative movement of the members into their unlocked relationship.

16. In an aircraft, a movable control surface, operating means for said surface connected thereto by a resilient play connection; locking means for the control surface comprising a first member connected by a first pivot to the aircraft and to a second member by a second pivot, a link connected by a third pivot to the second member and by a fourth pivot to the control surface, and resilient means connecting said members to urge them either into a locking relationship wherein the pivots are-substantially aligned or into an unlocked relationship wherein the third pivot is remote from a line between the first and fourth pivots permitting said members to swing about the first pivot in response to movement of the control surface; and unlocking means operable by and upon actuation of the operating means for moving the members into their unlocked relationship, said unlocking means including a part engageable with the first member to move the latter about the first pivot, upon actuation of the operating means in one direction, to effect relative movement of the members into their unlocked relationship, and said unlocking means also including another part engageable with the second member to move the latter about the second pivot, upon actuation of the operating means in the opposite direction, to effect relative movement of the members into their unlocked relationship. 7

JOHN P. NIX.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED, STATES PATENTS. Number 

